<!DOCTYPE HTML>
<html>

<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
  <title>无标题文档</title>
</head>

<body>
  <form>
    请选择你爱好:<br>
    <input type="checkbox" name="hobby" id="hobby1"> 音乐
    <input type="checkbox" name="hobby" id="hobby2"> 登山
    <input type="checkbox" name="hobby" id="hobby3"> 游泳
    <input type="checkbox" name="hobby" id="hobby4"> 阅读
    <input type="checkbox" name="hobby" id="hobby5"> 打球
    <input type="checkbox" name="hobby" id="hobby6"> 跑步 <br>
    <input type="button" value="全选" onclick="checkall();">
    <input type="button" value="全不选" onclick="clearall();">
    <p>请输入您要选择爱好的序号，序号为1-6:</p>
    <input id="wb" name="wb" type="text">
    <input name="ok" type="button" value="确定" onclick="checkone();">
  </form>
  <script type="text/javascript">
    function checkall() {
      var hobby = document.getElementsByTagName("input");
      console.log(hobby)
      for (let i = 0; i < hobby.length; i++) {
        if (hobby[i].type == "checkbox") {
          // console.log("+1")
          hobby[i].checked = "checked";
        }
      }
    }

    function clearall() {
      var hobby = document.getElementsByName("hobby");
      hobby.checked = "";
      // 任务2
      for (let i = 0; i < hobby.length; i++) {
        if (hobby[i].type == "checkbox") {
          // console.log("+1")
          hobby[i].checked = "";
        }
      }
    }

    function checkone() {
      var j = document.getElementById("wb").value;
      var numh = "hobby" + j;
      var temp = document.getElementById(numh);
      temp.checked = "checked"
      // 任务3

    }
  </script>
</body>

</html>